One of the bolt holes into my subframe where I'm putting in adjustable brackets is stripped. I was thinking bout tapping a larger thread into it? Anyone had this problem what size thread should I tap.

I believe the current thread is 5/16 UNF Fine.

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PrOuDlY aSkInG qUeStIoNs FoR uR aMuEsMeNt

If it's stripped, the hole is now 5/16".
This is the right size to tap out 3/8" UNC. You can then use a starter motor bolt like I did.
Grease the threads good when you bolt it up.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

5/16ths is the only UNF thread I know of you can do this, but you can tap it out 3/8 UNF and directly screw in a 5/16th UNF thread replacement (helicoil). You can buy them loose in bags of about 10 or 20 for cheap. You don't need a special helicoil tap as the threads per inch are the same for these two sizes.

Just be aware, if one thread is soft like cheese on those rear subframe captive nuts, then they're all the same.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

3/8 Unc or 3/8 Unf doc?

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1. You don't want a helicoil in there, if anything rusts you will be in trouble.
2. A bigger coarse thread in there is less likely to strip again.
2. A 3/8 UNC tap is way cheaper than a helicoil kit.


[edit] of course if you have a 3/8 UNF tap already I would tap it to that, fit a 3/8 UNF bolt and forgo the helicoil.

IMO helicoils are a last resort.. even in alloy.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I tapped a 3/8 UNF into one of mine - no worries, except it's hard to get a socket on it now because it's the one that sits closer to the subframe

Went around work picked up unc 3/8 taps. So I'll use that. Should be fun

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find some cutting fluid too

not sure if you've tapped holes before, but if not, practice on some scrap, or a 5/16 nut held in a vice or something.

Yeh I should be alright. Just one thing most of the thread is stripped but should I run a 3/8 " drill bit through to clean it all up?

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NO!!!!

but you can run a 5/16" drill bit through it

Do yourself a favour and fit 3/8 UNC Allen head bolts . No more strugling wth sockets that wont fit in the space. Even 3/8 sockets are a tight fit. Fit a high tensile washer under the bolt head. Just make sure the thread doesnt go behond the captive nut. Spray Shell ensis fluid ( transformer oil) through the bolt holes - get as much in as you can to stop the dredded red powder comming again. Coat the thread of the bolt as well

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Mk1 Cooper S
Mini K Rally car

Depending which one it is, fitting a bigger bolt may make it harder to do toe in / out adjustments as there won't be any play left in the hole on the bracket.

I helicoil them back to original. No odd bolts then. All these threads (welded root nuts in the subframs and body) I always give the bolts a smear of grease on the threads.

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Lol just re read that ... Duh!

Got that all done just b4 it got dark ... Wish I had a garage / shed....

Working in a carpark sucks.

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